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ac·tive (ăktĭv)
1. Being in physical motion: active fish in the aquarium.
2. Functioning or capable of functioning.
a. Marked by energetic activity; busy: active stock and bond markets; spent an active day sightseeing.
b. Involving or requiring physical exertion and energy: an active workout at the gym.
a. Being in a state of action; not quiescent: active hostilities along the border.
b. Erupting or liable to erupt; not dormant: an active volcano.
a. Marked by or involving direct participation: took an active interest in politics; played an active role on the committee.
b. Currently in use or effect: an active membership.
c. Openly acknowledged or expressed: an active dislike of the new neighbors.
6. Producing an intended action or effect: active ingredients.
7. Grammar
a. Indicating that the grammatical subject of a verb is performing or causing the action expressed. Used of a verb form or voice.
b. Expressing action rather than a state of being. Used of verbs such as run, speak, and move.
8. Of or relating to the management of an investment portfolio by continually making investment decisions based on new information as opposed to maintaining a predetermined strategy or reproducing the returns of a market or index.
9. Electronics
a. Being a source of electrical energy, as a generator.
b. Capable of converting or amplifying voltages or currents, as a diode or transistor.
10. Being on full military duty and receiving full pay.
1. Grammar
a. The active voice.
b. A construction or form in the active voice.
2. A participating member of an organization: union actives.

[Middle English actif, from Old French, from Latin āctīvus, from āctus, past participle of agere, to drive, do; see ag- in the Appendix of Indo-European roots.]

active·ly adv.
active·ness n.

Synonyms: active, busy, energetic, vigorous, dynamic, lively
These adjectives mean having or displaying energy. Active is the most general, connoting physical or mental exertion in a variety of contexts: an active toddler; an active imagination; remained active in later years by walking and swimming.
Busy suggests engagement in sustained activity on a particular task or job: a busy newspaper staff rushing to meet the deadline.
Energetic and vigorous emphasize performance of an activity or pursuit with enthusiasm or intensity: an energetic competitor; a vigorous crusader against drunk driving.
Dynamic connotes energy and forcefulness that often inspire others or bring about change: a dynamic leader who revitalized the party.
Lively suggests animated activity or alertness: a lively folk dance; a lively interest in politics.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.